﻿using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;

namespace My.Dotnet.Net
{
    /// <summary>
    /// 该包类特有的工具方法
    /// </summary>
    public static class Util
    {
        /// <summary>
        /// 将字典类型数据转化为Http请求时的URL参数
        /// </summary>
        /// <param name="paramDict">含有URL信息的键值对</param>
        /// <param name="type">转换URL数据的类型。如JSON 格式"{ }"，urlencode格式为:"x=&y="</param>
        /// <returns></returns>
        public static string ParamUrlEncode(Dictionary<string, string> paramDict, ContentType type)
        {
            StringBuilder sb = new StringBuilder();
            switch (type)
            {
                case ContentType.urlencoded:
                    foreach (KeyValuePair<string, string> kp in paramDict)
                    {
                        sb.AppendFormat("{0}={1}&", kp.Key, kp.Value);
                    }
                    sb.Replace("&", "", sb.Length - 1, 1);
                    break;
                case ContentType.json:
                    sb.Append("{");
                    foreach (KeyValuePair<string, string> kp in paramDict)
                    {
                        sb.AppendFormat("\"{0}\":\"{1}\",", kp.Key, kp.Value);
                    }
                    sb.Replace(",", "", sb.Length - 1, 1).Append("}");
                    break;
                case ContentType.xml:
                    break;
                default:
                    break;
            }
            return sb.ToString().Trim();
        }


        /// <summary>
        /// Http方式下载文件
        /// </summary>
        /// <param name="url">http地址</param>
        /// <param name="localfile">本地文件</param>
        /// <param name="isLocalFile">true 本地文件  false 网络应用文件</param>
        /// <returns></returns>
        public static bool Download(string url, string localfile)
        {
            bool flag = false;
            long startPosition = 0; // 上次下载的文件起始位置
            FileStream writeStream = null; // 写入本地文件流对象
                                           // 判断要下载的文件夹是否存在
            if (File.Exists(localfile))
            {

                writeStream = File.OpenWrite(localfile);             // 存在则打开要下载的文件
                startPosition = writeStream.Length;                  // 获取已经下载的长度
                writeStream.Seek(startPosition, SeekOrigin.Current); // 本地文件写入位置定位
            }
            else
            {
                writeStream = new FileStream(localfile, FileMode.Create);// 文件不保存创建一个文件
                startPosition = 0;
            }

            try
            {
                HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(url);// 打开网络连接

                if (startPosition > 0)
                {
                    myRequest.AddRange((int)startPosition);// 设置Range值,与上面的writeStream.Seek用意相同,是为了定义远程文件读取位置
                }


                Stream readStream = myRequest.GetResponse().GetResponseStream();// 向服务器请求,获得服务器的回应数据流


                byte[] btArray = new byte[512];// 定义一个字节数据,用来向readStream读取内容和向writeStream写入内容
                int contentSize = readStream.Read(btArray, 0, btArray.Length);// 向远程文件读第一次

                while (contentSize > 0)// 如果读取长度大于零则继续读
                {
                    writeStream.Write(btArray, 0, contentSize);// 写入本地文件
                    contentSize = readStream.Read(btArray, 0, btArray.Length);// 继续向远程文件读取
                }

                //关闭流
                writeStream.Close();
                readStream.Close();

                flag = true;        //返回true下载成功
            }
            catch (Exception ex)
            {
                writeStream.Close();
                flag = false;       //返回false下载失败
            }
            return flag;
        }
    }
}
